Supplementary funds are requested to enable us to continue working on the projects outlined in the renewal application NS 05572-10, and to undertake new investigations on plasma membranes of lymphoid cells, organotypic central or peripheral nervous (CNS or PNS) cultures and of murine neuroblastoma cells. Projects already outlined on NS 05572-10 are on: (1) clinical studies (psychomotor retardation-demyelinating disorders), (2) experimental studies, (a) studies on experimental allergic encephalomyelitis, (b) development of cortical synapses in normal and hypothyroid animals, (c) development of methods of cell affinity labeling using lectins or antibodies as probe molecules. In the new proposal we shall explore the feasibility of the application of the lactoperoxidase (LP) catalyzed iodination (I125) of plasma membranes of lymphoid cells, organotypic CNS or PNS cultures, and murine neuroblastoma cells. Quantitative ultrastructural autoradiographic studies will determine the site of I 125 incorporation at the end of iodination and after incubation in medium at 37 degrees centigrade (internalization of labeled plasma membrane). Myelin, synaptosome fractions and synaptosome membranes will be isolated from cultures, with carrier normal rat brain, and patterns of protein labeling will be examined in SDS-polyacrylamide gels by microdensitometry and autoradiography. Similar studies will be performed on crude membrane fractions of neuroblastoma cells. Studies on segregation and internalization of concanavalin A wheat-germ agglutinin and ricin labeled plasma membranes of the round and extended forms of neuroblastoma cells will be performed.